This retrospective cross-sectional study utilized data from the IBM MarketScan® Research database (Ann Arbor, MI, USA). Data were analyzed to assess trends in AS diagnostic prevalence focusing on the 11-year period from January 1, 2006 to December 31, 2016. AS diagnostic prevalence rates were analyzed for the total AS population and stratified by age and gender. Demographic variables and patient characteristics were assessed and the age-adjusted prevalence rate was measured and stratified for 2016 cohort.
IBM Marketscan Commercial, Medicaid and Medicare-Supplemental Claims database contains de-identified patient data including in-patient and outpatient physician visits, emergency room visits, procedures, and pharmacy prescriptions. Study variables were defined in the IBM Marketscan database using patient enrollment records and International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) and International Classification of Disease, 10th Revisions, Clinical Modification (ICD-10-CM) codes. In order to protect patient privacy, all data from the IBM Marketscan Research database are compliant to the Health Insurance Portability and Accountability Act (HIPAA).
Identification of AS
For each calendar year of analysis, a cohort was assembled that consisted of all AS patients that were 18 years or older on January 1st of the calendar year. Patients were required to have continuous enrollment in medical and pharmacy benefits throughout the calendar year, with the exception of an enrollment gap allowance of less than 30 days. Patients with at least one AS diagnostic code (ICD-9:720.0; ICD-10: M45.x) were identified from these cohorts.
Annual AS diagnostic prevalence was estimated using the US adult population in the IBM MarketScan® Research database during the 11-year period of 2006 to 2016. For each calendar year, a cohort was created and the AS case identification was applied. The numerator in the AS diagnostic prevalence estimation was the number of patients that met the AS definition described in the previous section. The denominator was the number of all patients over the age of 18 with continuous enrollment (during the calendar year) in the cohort.
AS diagnostic prevalence was estimated and stratified by gender (male and female) and age (< 25, 25–34, 35–44, 45–54, 55–64, and ≥ 65) for each calendar year from 2006 to 2016. Trends in treatments patterns of tumor necrosis factor inhibitors (TNFi) (adalimumab, infliximab, etanercept, golimumab, certolizumab pegol), secukinumab, Cox-2 inhibitor (celecoxib), sulfasalazine, methotrexate, acetaminophen, NSAIDs (aspirin, ibuprofen, meloxicam, nabumetone, diclofenac, naproxen, diflunisal, etodolac, fenoprofen, fluribiprofen, indomethacin, ketoprofen, ketorolac, meclofenamate, mefanamic, meprobamate, oxaprozin, piroxicam, sulindac, tolmetin, salsalate), muscle relaxants (cyclobenzaprine, orphenadrine, chlorzoxazone, methocarbamol, carisoprodol, metaxalone, dantrolene, baclofen, tizanidine), anticonvulsant (gabapentin, pregabalin, carbamazepine, topiramate, oxcarbazepine), opioids (codeine, oxycodone, hydrocodone, propoxyphene, dihydrocodeine, fentanyl, hydromorphone, levorphanol, methadone, morphine, oxymorphone, tramadol, tapentadol, meperidine, butorphanol, buprenorphine, nalbuphine, pentazocine), and oral and injectable glucocorticoids (betamethasone, cortisone, dexamethasone, hydrocortisone, methylprednisolone, prednisolone, prednisone, triamcinolone). Descriptive statistics of patient demographics and treatment patterns were conducted for the total AS cohort and male and female subgroups. Continuous variables were analyzed by means and standard deviations (SD) while categorical variables were analyzed by frequency counts and percentages (%).